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Biosynthesis of progesterone derived neurosteroids by developing avian CNS : in vitro effects on the gabaa receptor complex
Author(s) -
Pignataro Leonardo,
Lerner Alejandro A.Colman,
Barañao J.Lino,
De Plazas Sara Fiszer
Publication year - 1998
Publication title -
international journal of developmental neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.761
H-Index - 88
eISSN - 1873-474X
pISSN - 0736-5748
DOI - 10.1016/s0736-5748(98)00015-x
Subject(s) - neuroactive steroid , gabaa receptor , in vitro , allopregnanolone , chemistry , receptor , progesterone receptor , neuroscience , biology , endocrinology , medicine , biochemistry , estrogen receptor , cancer , breast cancer
It has been demonstrated in different vertebrate species that the GABA A receptor complex is modulated by certain steroids. Theses results prompted work on the synthesis of these neurosteroids in the Central Nervous System. However, there are scarcely any studies analyzing their production or their modulatory effects on this receptor during development. In this work, the biosynthesis of [ 14 C]progesterone metabolites as well as the characterization of their in vitro effects on the GABA A receptor complex in developing chick optic lobe were investigated. Studies on progesterone metabolism indicated that this steroid was converted to 5 β ‐pregnanedione, 5 β ‐pregan‐3 β ‐ol‐20‐one, and a 20‐hydroxy derivative. Radioactive progesterone was completely metabolized at early embryonic stages, and a great proportion of 5 β ‐pregnanedione was converted to 5 β ‐pregnan‐3 β ‐ol‐20‐one. Thus, it seems that some of the steroidogenic activities present in chick optic lobe are age‐dependent, though greater at embryonic stages. Results from in vitro modulation of [ 3 H]flunitrazepam binding by 5 β ‐pregnan‐3 β ‐ol‐20‐one indicated that this steroid produces a one‐component‐concentration dependent enhancement above control binding. 5 β ‐pregnan‐3 β ‐ol‐20‐one EC 50 values were 0.195±0.049, 0.101±0.017, 0.147±0.009, and 0.569±0.114 μ M, and E max were 22.37±1.57, 23.67±4.02, 29.01±1.08, and 15.11±2.67% at embryonic days 11, 14, hatching, and postnatal day 21, respectively. In conclusion, the biosynthesis of 5 β ‐pregnan‐3 β ‐ol‐20‐one from progesterone in developing chick optic lobe, together with its ability to modulate the GABA A receptor present in such tissues, suggests a physiological role of this neurosteroid in developing avian Central Nervous System.